Water craft with aerodynamic lift

ABSTRACT

A water craft which is designed to operate as a surface craft at slow speed, and to cruise at higher speeds in a semi-flying condition within the &#39;&#39;&#39;&#39;ground effect&#39;&#39;&#39;&#39; zone close to the surface of the water has a body of high lift airfoil sectional shape and a pair of relatively short, preferably folding wings. An integral pontoon extends downwardly along each side of the body, and a downwardly sloping, rearwardly extensible vane is housed in the after end of the body. Four takeoff skis are flush-mounted, one near the bow and one near the stern in the bottom of each pontoon. These takeoff skis are pivotally mounted at their forward ends and are resiliently biased to swing downwardly about their pivotal mountings. A winch cable and hydraulic cylinders control pivotal positioning of these take-off skis. Four cruising skis also are provided, one outboard of each takeoff ski, to provide planing support for a portion of the weight of the craft when the latter is in its high speed cruising attitude. An engine driven airscrew propels the craft when in said cruising attitude, while auxiliary water jet drive means propels the craft when it is supported by flotation of the pontoons on the water.

United States Patent [1 1 Raynes 1 *Oct. 2, 1973 1 1 WATER CRAFT WITH AERODYNAMIC LIFT [75] Inventor: Burt F. Raynes, Chula Vista, Calif.

[73] Assignee: Rohr Corporation, Chula Vista,

Calif.

[*1 Notice: The portion of the term of this patent subsequent to Aug. 2. 1989 has been disclaimed.

[22] Filed: July 27, 1970 211 Appl. No.: 58,617

[52] US. Cl. 114/66.5 H

[51] Int. Cl B63b 1/22 [58] Field of Search 114/665 [56] References Cited UNITED STATES PATENTS 1,156,215 10/1915 Curtiss 114/665 3,145,954 8/1964 Jenny et al 114/665 X Primary Examiner-Milton Buchler Assistant Examiner-Barry L. Kelrnachter Attorney-George E. Pearson [57] ABSTRACT A water craft which is designed to operate as a surface craft at slow speed, and to cruise at higher speeds in a semi-flying condition within the ground effect" zone close to the surface of the water has a body of high lift airfoil sectional shape and a pair of relatively short, preferably folding wings. An integral pontoon extends downwardly along each side of the body, and a downwardly sloping, rearwardly extensible vane is housed in the after end of the body.

Four takeoff skis are flush-mounted, one near the bow and one near the stern in the bottom of each pontoon. These takeoff skis are pivotally mounted at their forward ends and are resiliently biased to swing downwardly about their pivotal mountings. A winch cable and hydraulic cylinders control pivotal positioning of these take-off skis.

Four cruising skis also are provided, one outboard of each takeoff ski, to provide planing support for a portion of the weight of the craft when the latter is in its high speed cruising attitude. An engine driven airscrew propels the craft when in said cruising attitude, while auxiliary water jet drive means propels the craft when it is supported by flotation of the pontoons on the water.

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ATTORNEY WATER CRAFT WITH AERODYNAMIC LIFT BACKGROUND OF THE INVENTION In the field of water craft there are two basic types of hulls. One, the displacement type hull, is constantly buoyed up by the displacement of an amount of water substantially equal to the weight of the craft. The other, the planing type hull, has the bottom of its hull shaped to exert a lifting effect, which, at a speed determined by loading and other factors, causes the bull to rise and skim or plane along substantially on the surface of the water, thereby greatly reducing drag.

A more recent development in water craft is the hydrofoil, which has a plurality of lifting vanes or foils mounted on struts, extending downwardly from the hull into the water. At speeds determined by loading and other factors the hull rises clear of the water, being supported entirely by the lifting or planing effect of the vanes or foils.

It is well known that when an airplane is close to the ground or water, as in landing and taking off, the lift is increased substantially and drag is reduced due to a compressive effect exerted on the air between the aircraft and the ground or water therebeneath. This effect is referred to as ground effect and is an important factor in the present invention.

SUMMARY OF THE INVENTION It is a primary objective of this invention to provide a water craft which, when at rest, and at slow and intermediate speeds, is supported by floatation means, and in such condition is propelled and steered by boat type propulsion means. The craft also has airfoil lifting means, airplane type propulsion means, and adjustable skis, so that under defined cruising conditions of craft weight and air speed an aerodynamic lift is created, which, in combination with a planing effect exerted by the skis, lifts the craft into a semi-flying condition in the ground effect zone, a few feet above the surface of the water.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing objectives and advantages of the invention will be apparent from the following description and the accompanying drawings, wherein:

FIG. 1 is a perspective view of a craft embodying the I invention as it appears when cruising.

FIG. 2 is a fragmentary bottom view of the starboard pontoon of the craft shown in FIG. 1 and portions of the wing and body adjacent thereto.

FIG. 3 is a side elevational view of the craft shown in FIGS. 1 and 2, the takeoff skis being shown in solid lines in stowed position, the forward port takeoff ski being also shown in dot-dash lines in takeoff position, and in two-dot-dash lines in emergency braking condition, while the after port cruising ski is shown in broken lines in its forwardly tilted position.

FIG. 4 is a fragmentary, front, elevational view of the port half of the craft shown in FIGS. 1 3, the stern vane being'shown in extended position in broken lines, the forward takeoff ski being shown as in FIG. 3, and the port wing being broken away.

FIG. 5 is an enlarged, fragmentary, perspective view of the forward, starboard corner portion of the body and its integral pontoon, portions being broken away.

FIG. 6 is an enlarged, fragmentary, side, elevational view of a cruising ski and its mounting strut, the ends of the ski and portions of the strut cylinder and its fairing being broken away.

FIG. 7 is a top end view of the crusing ski mounting strut looking in the direction of the arrows 7-7 in FIG. 6. 114

FIG. 8 is a fragmentary sectional view taken along line 8-8 of FIG. 7, the strut mounting shaft being broken away.

FIG. 9 is a fragmentary sectional view taken along line 9-9 of FIG. 6, portions being broken away.

FIG. 10 is a fragmentary sectional view taken along line 10-10 of FIG. 7, the piston rod being broken away.

DETAILED DESCRIPTION Referrring to the drawings in detail, an illustrative water craft A embodying the invention comprises a body 11 of high lift airfoil sectional shape and a pair of relatively short folding Wings 12 and 13, with a combined wing-flap and aileron 14 mounted on each wing. Conventional control means, not shown, are operatively connected to the flap-ailerons 14 for operating either in the same direction as wing flaps, or in opposite directions as ailerons, as required. The body 11, wings I2 and 13 and flap-ailerons 14 are constructed in accordance with conventional aircraft practice, and since the details of such construction are well known to those familiar with the aircraft industry, and are not per se a feature of the present invention, such details are omitted.

A plurality of ports or windows 15 are provided across the forward end and along each side of the body 11, and also in the rear as desired.

Integral pontoons l7 and 18, best shown in FIG. 5, are provided, one thereof projecting downwardly along each side of the crafts body 11. These pontoons are of suitable, light weight, boat type construction, with light frames 19, FIG. 5, notched to receive stringers 20 and covered with a suitable skin 21 which may be of aluminum or honeycomb panel.

An engine mount 22 is provided on top of the body 11 in accordance with conventional seaplane and amphibious aircraft practice, and a pair of suitable aircraft types engines 23 and 24 are mounted thereon. As illustrated these engines comprise a pair of aircraft type,tur-' bines interconnected by suitable or conventional gearing to drive a single airscrew type propeller 25.

A rearwardly extensible flap type vane 27 is housed in the after portion of the body 11, and is roller mounted on channel tracks 28, see FIG. 3, for extension and retraction by a ball type screw 29 in the manner of a well known type of airplane wing-flap. The vane 27 preferably is retracted fully when the craft A is at rest and when traveling at slow speed, except when heading into a high wind, at which time it may be expeditious to extend the vane at least part way. When cruising as shown in FIG. I, and when taking off, the vane 27 is extended as required to provide additional lift and also to control trim and thereby prevent the craft from becoming completely airborne. The vane 27 may be actuated by conventional mechanical, hydraulic or electrical mechanism as desired, and such actuating mechanism may be controlled either manually by the pilot of the craft, or automatically, as desired.

In the stern of each pontoon l7 and 18, see FIGS. 2 and 3, there is installed a conventional water jet type boatpropulsion mechanism 30, such as Berkeley Jet Drive Unit. Each of these mechanisms comprises an axial flow, impeller type pump, not shown, which draws water from the body of water upon which the craft is floating, through an inlet in the bottom of the pontoon, and discharges this water rearwardly through the usual nozzle 31 in the form of a high velocity jet. The reactance to the waterjet discharge drives the craft forward in a well known manner. The jet nozzle 31 is dirigible laterally for steering purposes, and is provided with a usual thrust reversing scoop 32, which, when lowered to cover the jet, diverts the jet and directs it forwardly beneath the pontoon when it is desired to drive the craft astern. The water jet propulsion mechanisms may be powered either by an auxiliary engine, not shown, in a conventional manner, or by conventional mechanical, electrical or hydraulic transmission mechanism from the main engine or engines 23 and 24. Since the various structural and operational details pertaining to the water jet propulsion mechanism 30 will be readily apparent to any routine designer or engineer familiar with such mechanisms, and since such details are not per se a feature of the present invention, they are omitted herein.

Two separate and distinct sets of ski-like planing members are provided.

One set, four in number and referred to herein as the takeoff skis 33 are flush-mounted in the bottoms of the pontoons, one near the bow and one near the stern of each pontoon.

The other set, also four in number and referred to herein as the cruising skis 34 are mounted one outboard of each takeoff ski.

Each takeoff ski 33, see FIGS. 2 5, comprises a wide rear portion 35, shaped to fit into a recess 36 provided therefor in the bottom of its respective pontoon, and to fit flush with the pontoon bottom when stowed therein, and a narrow, upwardly curved forward end mounting portion 37. The forward end portion 37 is pivotally mounted in the forward end of its respective recess 36 by a resiliently torque-biased bushing known as a Torsilastic Bushing 38 made by B. F. Goodrich Co., to be described briefly later herein. In the unstressed or normal condition of its Torsilastic Bushing, each takeoff ski 33 is substantially upright, as shown in dash-two-dot lines 33a for the forward ski in FIGS. 3 and 4. The takeoff skis 33 are drawn by a winch 39, see FIG. 5, rearwardly and upwardly from their normal, upright, emergency braking position to either their angularly disposed takeoff position shown in dash-dot lines 33b for the forward ski in FIG. 3, or to their stowed position shown in solid lines 330 in that same figure. The winch 39 is mounted on a pontoon bulkhead 40 and is connected to the takeoff skis 33 by a cable 41 wound on the winch drum-39a, see FIG. 5. The winch drum 39a is driven by suitable reversible drive means, such as a conventional hydraulic or geared electric motor 42, which is operatively connected to the winch drum by a suitable clutch 43 embodying quick release mechanism, for example, an electric clutch. Preferably the clutch release mechanism is arranged to release either all four or any selected opposite two of the takeoff skis 33 simultaneously, which balances the braking effect produced by the skis and avoids swerving.

The clutch 43 is arranged to release the winch drum 39a automatically when a lever 44, mounted on the bow of each pontoon above normal water level, is hit by solid water in the event that a dangerously big wave should be encountered while the craft is in cruising attitude as shown in FIG. 1. Actuation of the lever 44 under such emergency condition actuates a switch 45, which closes a circuit to release the clutch 43 and free the winch drum 39a, thereby allowing the cable 41 to run and permit the takeoff skis 33 to swing down, under the torque bias of their Torsilastic bushings, to their normal, upright, emergency braking positions.

For providing back-up support for the take-off skis 33 when the latter are extended to their take-off positions 33b, see FIG. 3, a pair of hydraulic cylinders 47 are fixedly mounted in generally axially upright position on a bulkhead 40 above the rear portion of each takeof ski 33. The lower ends of the piston rods of these hydraulic cylinders bear on thrust plates 48 attached to the upper side of each takeoff ski 33. Extension of the piston rods of these cylinders 47 provides back-up support for the take-off skis to resist the frequently substantial stresses imposed on these skis during takeoff.

The cruising skis 34 are of strong, slightly flexible material as used, for example, in conventional water skis. Each cruising ski 34 is mounted on resiliently torque biased means such as a Torsilastic Bushing 49 on the lower end of the piston rod 50 of a fore-and-aft tiltable, oleo strut 51, see FIGS. 1 6, of a type well known in aircraft construction.

Each Torsilastic Bushing 49, see FIG. 10, comprises a bushing 49a of tough, resilient rubber or rubber-like material fused to a metal hub 52, and also to an enclosing metal sleeve 53. The hub 52 is fixedly secured to a mounting pin 54 anchored to each cruising ski 34, while the enclosing sleeve 53 is fixedly secured within an eye 55 on the lower end of the strut piston rod 50. Thus, any pivotal movement of a crusing ski 34 about its mounting axis causes a torsional displacement of its rubber or rubber-like bushing 49a which resiliently urges such ski 34 back toward its normal relative angular position shown in FIG. 6. A pointer 57, see FIGS. 6 and 10, on an upward extension of one side of each cruising ski 44 overlies a scale 58 on the enclosing sleeve 53 of its Torsilastic Bushing 49 to indicate the amount of angular displacement of the ski 34 from its normal position.

The piston rod 50 of each oleo strut 51 is splined at 59 for axial slidable movement within a correspondingly internal splined steering disk 60, which is fitted for rotative steering movement into a circular recess provided therefor in the underside of a flange 61 fixedly secured to the lower end of the hydraulic cylinder 62 of each oleo strut 51. The steering disk 60 is retained in its recess by two plates 63, which overlie the edge of their associated steering disk 60 and are secured to the flange 61 by machine screws 64.

For controlled steering movement of the disk 60, a pair of upstanding pins 67 and 68, see FIG. 8, are secured thereto on diametrically opposite sides of the axis thereof. These pins ride, respectively, in co-axially curved slots in the flange 61, and the upper ends of the pins are respectively connected to the piston rods of a pair of hydraulic steering cylinders 69 and 70 mounted on the flange 61. Selective operation of the hydraulic cylinders 69 and 70 by means of usual hydraulic controls, not shown, turns the disk 60, and with it the splined piston rod 50 fitted therein, and the attached cruising ski 34, as required.

Each oleo strut piston rod 50 is connected at its upper end, through a conventional shock absorber 71 to its associated piston 72. The admission of pressurized hydraulic fluid through a usual high pressure hydraulic hose 73 to the oleo strut cylinder 62 above the piston 72 extends the piston 72 and the piston rod 50 with the cruising ski 34 attached thereto; while the introduction of pressurized fluid through a hose 75 to the cylinder below the piston 72 retracts these members. The shock absorber 71 operates in a conventional manner by means of a coil spring 77 and a damping plate 78 having an orifice 79 therein.

For mounting the struts 51 on the body 11 each oleo strut cylinder 62 has a bearing extension 80 (FIG. 9) secured to extend at right angles to the strut axis, which bearing extension is journaled on roller bearings 81 on a cantilever stub shaft 82 secured by mounting 83 to a fixed structural part 84 of the crafts body 11.

For selectively tilting the struts 51 and their respective cruising skis 34 fore and aft, gear segment 85 is fixedly secured co-axially to each bearing extension 80 and is in mesh with a rack 89 actuated by the piston rod of a conventional hydraulic cylinder 90, see FIG. 5. Conventional hydraulic controls, not shown, control operation of the hydraulic cylinder 90 to tilt the oleo struts fore and aft between desired limits, for example, between the two positions illustrated for the stern cruis ing ski in FIG. 3.

OPERATION In operating the craft A with the pontoons l7 and 18 floating on a supporting body of water, propulsion of the craft A usually will be by means of the-water jet drive mechanism 30. During each operation the takeoff skis 33 are stowed flush with the bottoms of their respective pontoons, the cruising skis 34 are retracted and tilted forwardly to a position substantially parallel to the surface of the water, and are pointed straight ahead, and the craft A is manipulated in a manner generally similar to a conventional catamaran or other. twin-hull craft having a water jet drive mechanism in each hull. When so operating the craft, care must be exercised to prevent it from becoming completely airborne, and for this reason the air speed must be carefully observed, and when takeoff air speed is approached the vane 27 should be extended as required to insure proper trim control, and further acceleration probably should be avoided.

When it is desired to elevate the craft A to cruising attitude as shown in FIG. 1, the drive is switched from water jet to air drive by means of the engines 23 and 24 and propeller 25 and the cruising skis 34 are tilted to tip-high position as shown in FIG. 1 by means of their tilt control cylinders 90, FIG. 5. 7

With the craft A preferably headed into the wind, the throttles controlling the engines 23 and 24 are advanced, and as the craft gains momentum the takeoff skis 33 are gradually lowered to their full takeoff positions shown in dash-dot lines 33b in FIG. 3 by actuation of their back-up hydraulic cylinders 47. At the same time the cruising skis 34 are gradually extending by means of their oleo strut hydraulic cylinders 62. The aerodynamic lift exerted by the body 11 and wings 12 and 13, plus the planing lift of the takeoff skis 33 and cruising skis 34 raise the craft initially onto the takeoff skis 33, and then into the full cruising attitude on the cruising skis 34 as shown in FIG.- 1, at which point the takeoff skis 33 may be retracted.

In its cruising attitude the airfoil body 11 and wings l3 and 14 are so close to the underlying body of water B, see FIG. 1, that the ground effect referred to previously herein provides high aerodynamic lift and low drag for the craft which is airborne except for the cruising skis 34, the latter remaining in planing contact with the water B. The aerodynamic lift, however, diminishes rapidly with any increase in the height of the craft above the water which would elevate it beyond the ground effect" zone, while the planing lift provided by the cruising skis 34 drops to zero in the event that they should leave the water. Both of these characteristics combine to provide a built-in safety factor which tends to keep the craft from becoming completely airborne. The craft is so designed that at an assigned cruising and air speed approximately percent of the craft's weight is borne by the aerodynamic lift of the body 11 and wings l2 and 13 combined, while the remaining I0 percent is provided by the cruising skis 34.

For turning the craft A while in its cruising attitude shown in FIG. 1, the craft should be banked as required by means of the flap-ailerons 14 to decrease the lift of the inside wing and to increase the lift of the outside wing on the turn, thereby increasing the draft exerted by the inside cruising skis 34 and decreasing the drag on the outside cruising skis as required. At the same time the cruising skis should be turned by means of their steering cylinders 69 so that they maintain a posi' tion substantially tangent to the turn.

In the event that the waves increase to dangerous height while the craft is in cruising attitude, and the safety lever 44 encounters solid water, it is swung rearwardly, thereby actuating the clutch release switch 45 to release the clutch 43, thereby freeing either all, or either laterally opposite two of the take-off skis 33 to swing downwardly under the torque bias of their Torsilastic Bushings to emergency braking positions 33a, see FIG. 3. The resiliently biased take-off skis in this position provide a powerful arresting force which quickly lowers the craft onto the surface of the water where it is supported by the pontoons l7 and 18.

The invention provides a water craft having aerodynamic characteristics which is capable of sure, safe and easy manipulation at slow speed and in cramped quarters when required, and at the same time is capable of cruising at high speeds with low drag, and free in largepart from buffeting action by waves.

Having illustrated and described my invention, I now claim and desire to protect by United States Letters Patent:

1. A water craft for operating in partially airborne condition within the ground effect zone of the atmosphere comprising a body of airfoil sectional shape a wing extending laterally from each side of the body,

a control element mounted on each wing for varying the lift of each wing,

flotation means providing floating support for the craft when on the surface of a body of water,

pitch control airfoil means for inducing a nose-down attitude to prevent the craft from becoming completely airborne,

a plurality of downwardly extensible and retractible cruising skis mounted in laterally spaced pairs, one pair near the forward and one pair near the rear end, respectively, of the body,

control means operatively connected to selectively extend and retract each cruising ski, and

aircraft type power drive means for propelling the craft at a speed at which the body and wings provide a major portion of the lift, and the cruising skis provide the remaining portion of the lift required to support the craft with its body and wings in the ground effect layer of the atmosphere, the pontoon means clear of the water, and the cruising skis planing on the water.

2. A water craft for operation in partially airborne condition within the ground effect" zone of the atmosphere comprising,

a body,

airfoil means on the body for exerting lift,

flotation means attached to the body for supporting the craft on the surface of a body of water, means for controlling the lateral attitude of the craft, means for controlling the pitch attitude of the craft, a plurality of cruising skis mounted in laterally spaced pairs, one pair at the forward end and one pair at the rear end, respectively, of the body,

aircraft type power drive means for propelling the craft at an air speed wherein the lift exerting airfoil means exert a lifting force equal to a substantial portion, but less than all of the weight of the craft,

means for tilting the cruising skis fore and aft, and

means for extending the cruising skis downwardly below the flotation means for exerting a planing, lifting force equal to the remainder of the weight of the craft for lifting the flotation means clear of the water for cruising operation.

3. A water craft as claimed in claim 2 wherein the airfoil means for exerting lift comprise, at least in part, an airfoil shaped body.

4. A water craft as claimed in claim 2 wherein the means for controlling the lateral attitude of the craft comprises means for retracting and extending selected ones of the cruising skis.

5. A water craft as claimed in claim 2 wherein the means for controlling the pitch attitude of the craft comprises an extensible and retractable downwardly and rearwardly inclined vane housed, in its retracted condition, within the after end of the body.

6. A water craft as claimed in claim 2 wherein the airfoil means for exerting lift comprises, at least in part, a pair of wings extending one from each side of the body.

7. A water craft as claimed in claim 6 wherein the means for controlling the lateral attitude of the body comprises a pair of ailerons mounted one on each wing.

8. A water craft as claimed in claim 7 wherein said ailerons are selectively operated simultaneously in different directions as ailerons and in the same direction as wing flaps.

9. A water craft as claimed in claim 2 wherein the flotation means comprises a pair of pontoons, one of said pontoons extending downwardly below the body in laterally spaced relation and at equal distances from the longitudinal center line of the craft.

10. A water craft as claimed in claim 9 wherein a water reaction type power propulsion means is provided in the stern of each pontoon.

11. A water craft as claimed in claim 10 wherein each propulsion means is of the water jet type.

12. A water craft as claimed in claim 2 wherein each ski is pivotally mounted on the end of the piston rod of an oleo strut for tilting movement about an axis at right angles to the strut axis, and resilient means control the tilt angle of each ski relative to its piston rod.

13. A water craft as claimed in claim 12 wherein each resilient means comprises a Torsilastic Bearing.

14. A water craft as claimed in claim 12 wherein steering means is operatively connected to each ski for pivotal movement of said ski about the axis of its mounting strut.

15. A water craft as claimed in claim 14 wherein the steering means comprises a plate in splined, axially sliding relation with each strut each of said plates being mounted on one of the struts for pivotal movement about the cylinder axis, and hydraulic control means are operatively connected to each of said plates for controlled steering movement of said each plate and the piston rod and ski associated therewith.

16. A water craft as claimed in claim 2 wherein a takeoff ski is mounted on each side of the craft to assist in raising the pontoons clear of the water.

17. A water craft as claimed in claim 16 wherein two takeoff skis are mounted on each side of the body, one near the forward end and one near the after end thereof.

18. A water craft as claimed in claim 17 wherein each takeoff ski is flush mounted in the bottom of the flotation means and is pivotally connected at its forward end thereto.

19. A water craft as claimed in claim 18 wherein means resiliently biases each takeoff ski to swing downwardly and forwardly about its pivotal support connection toward an upright position, and control means is operatively connected to each ski to control its angular position.

20. A water craft as claimed in claim 19 wherein the means resiliently biasing each takeoff ski toward an upright position is a Torsialastik Bearing.

21. A water craft as claimed in claim 19 wherein the control means for limiting the angular position of each takeoff ski comprises a winch mounted on the craft, and a winch cable wound on the winch and connected to said each takeoff ski at a point remote from the pivotal mounting axis of said each takeoff ski to the flotation means.

22. A water craft as claimed in claim 19 wherein a hydraulic cylinder is mounted above each ski and is provided with an extensible piston rod positioned to bear on the ski at a point remote from the pivotal sup port axis of the ski to provide backup support for the resilient biasing means during takeoff of the craft. 

1. A water craft for operating in partially airborne condition within the ''''ground effect'''' zone of the atmosphere comprising a body of airfoil sectional shape a wing extending laterally from each side of the body, a control element mounted on each wing for varying the lift of each wing, flotation means providing floating support for the craft when on the surface of a body of water, pitch control airfoil means for inducing a nose-down attitude to prevent the craft from becoming completely airborne, a plurality of downwardly extensible and retractible cruising skis mounted in laterally spaced pairs, one pair near the forward and one pair near the rear end, respectively, of the body, control means operatively connected to selectively extend and retract each cruising ski, and aircraft type power drive means for propelling the craft at a speed at which the body and wings provide a major portion of the lift, and the cruising skis provide the remaining portion of the lift required to support the craft with its body and wings in the ''''ground effect'''' layer of the atmosphere, the pontoon means clear of the water, and the cruising skis planing on the water.
 2. A water craft for operation in partially airborne condition within the ''''ground effect'''' zone of the atmosphere comprising, a body, airfoil means on the body for exerting lift, flotation means attached to the body for supporting the craft on the surface of a body of water, means for controlling the lateral attitude of the craft, means for controlling the pitch attitude of the craft, a plurality of cruising skis mounted in laterally spaced pairs, one pair at the forward end and one pair at the rear end, respectively, of the body, aircraft type power drive means for propelling the craft at an air speed wherein the lift exerting airfoil means exert a lifting force equal to a substantial portion, but less than all of the weight of the craft, means for tilting the cruising skis fore and aft, and means for extending the cruising skis downwardly below the flotation means for exerting a planing, lifting force equal to the remainder of the weight of the craft for lifting the flotation means clear of the water for cruising operation.
 3. A water craft as claimed in claim 2 wherein the airfoil means for exerting lift comprise, at least in part, an airfoil shaped body.
 4. A water craft as claimed in claim 2 wherein the means for controlling the lateral attitude of the crafT comprises means for retracting and extending selected ones of the cruising skis.
 5. A water craft as claimed in claim 2 wherein the means for controlling the pitch attitude of the craft comprises an extensible and retractable downwardly and rearwardly inclined vane housed, in its retracted condition, within the after end of the body.
 6. A water craft as claimed in claim 2 wherein the airfoil means for exerting lift comprises, at least in part, a pair of wings extending one from each side of the body.
 7. A water craft as claimed in claim 6 wherein the means for controlling the lateral attitude of the body comprises a pair of ailerons mounted one on each wing.
 8. A water craft as claimed in claim 7 wherein said ailerons are selectively operated simultaneously in different directions as ailerons and in the same direction as wing flaps.
 9. A water craft as claimed in claim 2 wherein the flotation means comprises a pair of pontoons, one of said pontoons extending downwardly below the body in laterally spaced relation and at equal distances from the longitudinal center line of the craft.
 10. A water craft as claimed in claim 9 wherein a water reaction type power propulsion means is provided in the stern of each pontoon.
 11. A water craft as claimed in claim 10 wherein each propulsion means is of the water jet type.
 12. A water craft as claimed in claim 2 wherein each ski is pivotally mounted on the end of the piston rod of an oleo strut for tilting movement about an axis at right angles to the strut axis, and resilient means control the tilt angle of each ski relative to its piston rod.
 13. A water craft as claimed in claim 12 wherein each resilient means comprises a Torsilastic Bearing.
 14. A water craft as claimed in claim 12 wherein steering means is operatively connected to each ski for pivotal movement of said ski about the axis of its mounting strut.
 15. A water craft as claimed in claim 14 wherein the steering means comprises a plate in splined, axially sliding relation with each strut each of said plates being mounted on one of the struts for pivotal movement about the cylinder axis, and hydraulic control means are operatively connected to each of said plates for controlled steering movement of said each plate and the piston rod and ski associated therewith.
 16. A water craft as claimed in claim 2 wherein a takeoff ski is mounted on each side of the craft to assist in raising the pontoons clear of the water.
 17. A water craft as claimed in claim 16 wherein two takeoff skis are mounted on each side of the body, one near the forward end and one near the after end thereof.
 18. A water craft as claimed in claim 17 wherein each takeoff ski is flush mounted in the bottom of the flotation means and is pivotally connected at its forward end thereto.
 19. A water craft as claimed in claim 18 wherein means resiliently biases each takeoff ski to swing downwardly and forwardly about its pivotal support connection toward an upright position, and control means is operatively connected to each ski to control its angular position.
 20. A water craft as claimed in claim 19 wherein the means resiliently biasing each takeoff ski toward an upright position is a Torsialastik Bearing.
 21. A water craft as claimed in claim 19 wherein the control means for limiting the angular position of each takeoff ski comprises a winch mounted on the craft, and a winch cable wound on the winch and connected to said each takeoff ski at a point remote from the pivotal mounting axis of said each takeoff ski to the flotation means.
 22. A water craft as claimed in claim 19 wherein a hydraulic cylinder is mounted above each ski and is provided with an extensible piston rod positioned to bear on the ski at a point remote from the pivotal support axis of the ski to provide backup support for the resilient biasing means during takeoff of the craft. 